Finding Center

mlfj4901 · Post by **mlfj4901** » Mon Jul 31, 2006 11:27 pm

Greetings,

I'm planning on removing my dob mirror in the next couple of days to mark the center. One question. What is the most accurate way for me to find and mark the center? I know when I find it I should put a 3 ring binder reenforcement ring around it, but I'm not sure what the best way to find it is.

Do I simply use a ruler?

-matt 8" skyquest dob

Ben Mullin · Post by **Ben Mullin** » Tue Aug 01, 2006 12:00 am

My method.

1. Use a compass (the circle drawing kind) to draw a circle the same diameter as your mirror on a piece of paper.
2. Cut out the circle.
3. Fold the circle in half.
4. Fold the folded circle in half again.
5. Snip off the point of the now pie shaped piece of paper.
6. Unfold the paper and center over your mirror. The hole should be in the center of your mirror.

It worked for me.

Ben

Jon Hickman · Post by **Jon Hickman** » Tue Aug 01, 2006 9:48 am

Matt:

Here's another method that works well, and only requires a plastic school ruler and a dry erase marker.

Lay the ruler across the mirror and draw a short line at the center point. Rotate the ruler and repeat, and repeat again. The intersection of the 3 short line segments is the center point of your mirror. Center your dot there, and wipe the line segments off with a Kleenex or your finger.

BTW, for those gasping in horror at writing on the mirror and then touching it with your finger, the center portion is obstructed by the secondary and does not affect the performace of the telescope.

mlfj4901 · Post by **mlfj4901** » Tue Aug 01, 2006 10:50 pm

Greetings,

Thanks, I think I might do both, just to make sure I get it right. Afterall I'll hopefully be using this center spot for quite awhile and would hate to be off for a couple of years....of course my wife says I've been slightly off for awhile....(saw that one coming didn't ya?).

Anyway, I think I'll use both since I'll have to swing by and pick up the required school supplies needed anyway. Do they even use compasses in school anymore?

-matt

Jon Hickman · Post by **Jon Hickman** » Wed Aug 02, 2006 9:39 am

mlfj4901 wrote:Do they even use compasses in school anymore?

-matt

One would wonder especially regarding "moral" compasses....

rallen911 · Post by **rallen911** » Wed Aug 02, 2006 8:25 pm

Matt,

Did you get a new mirror for your dob?

My Orion came with a center mark already on it. I was just wondering.

mlfj4901 · Post by **mlfj4901** » Wed Aug 02, 2006 11:27 pm

No, my Orion was bought used from some college kid. No center mark, no 2" eyepiece either.

Guess I need a new (and bigger) scope....

-matt